[health] Richer health payload, aligned with health://checks #71

Depends on: Issue #63

Summary

health://status returns only {name: "healthy" | "unhealthy" | "error: …"}. The TypeScript SDK serves a fuller payload, and its transform telemetry will need a place to go.

Reference

• ts:core/health/health-checks.resource.ts (health://checks, "Health Checks & Pipeline Telemetry"),
• ts:core/health/health.interface.ts (ServerHealthPayload, TransformTelemetry).

Scope

• Overall status; per check: status, latency and message; uptime; SDK version.
• Per-check timeout: a hanging check reports unhealthy and does not block the resource.
• A typed extension point for transform telemetry (Issues 1–5).
• Decide whether to also serve health://checks for parity, keeping health://status working.

Acceptance criteria

• Healthy, degraded and failing checks are reflected correctly in the payload.
• A check exceeding its timeout is reported within the timeout, and the other checks still run.
• The existing health://status consumers keep working, or the change is documented as breaking.